4-(2,6-Dialkylphenylamino)-3-alkoxy-2-butenoic acid and their use as herbicides

ABSTRACT

A compound having the structural formula ##STR1## wherein R is C 1  -C 4  alkyl; R 1  is C 1  -C 4  alkyl; R 2  is hydrogen or methyl; R 3  is methyl or ethyl; and R 4  is C 1  -C 4  alkyl.

BACKGROUND OF THE INVENTION

The present invention relates to certain butenoic acid compounds which are especially useful as post-emergent herbicides against annual and perennial grasses and broadleaf weeds. The compounds are especially useful in controlling weeds in rice, paddy water, post-emergent and post-flood.

Herbicides are widely used by farmers, commercial agricultural companies, and other industries in order to increase crop yields for such staple crops as corn, soybeans, rice, and the like, and to eliminate weed growth along highways, railroad rights-of-way, and other areas. Herbicides are effective in killing or controlling vegetation which compete for soil nutrients with the crop plants, and by reason of the fact that they control undesired vegetation.

There are a number of different types of herbicides presently sold commercially, and these fall into two general categories. These categories are pre-emergence and post-emergence herbicides. The pre-emergence herbicides are normally incorporated into or applied to the soil prior to the emergence of the undesired vegetation and the post-emergence herbicides are normally applied to the undesirable vegetation or to the soil surface where it is growing.

DESCRIPTION OF THE INVENTION

This invention relates to 4-(2,6-dialkylphenylamino)-3-alkoxy-2-butenoic acid as herbicides. The novel compounds of this invention have the following structural formula ##STR2## wherein R is C₁ -C₄ alkyl, preferably methyl or ethyl;

R¹ is C₁ -C₄ alkyl, preferably methyl or ethyl;

R² is hydrogen or methyl, preferably hydrogen;

R³ is methyl or ethyl; and

R⁴ is C₁ -C₄ alkyl, preferably methyl or ethyl.

In the above description of the compounds of this invention alkyl includes both straight and branched configurations; for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, and tert-butyl.

The compounds of this invention are active pre-emergence of pre-plant herbicides that are especially useful in controlling undesired grasses. The method of controlling undesirable grasses comprises applying an herbicidally effective amount of the above-described compounds to the area where control is desired either pre-emergence or pre-plant.

The compounds of the present invention can be prepared by the following general method: ##STR3##

The 4-bromo-3-alkoxy crotonate ester can be prepared by the teaching in J. Am. Chem. Soc., 1975, 97, 2503.

Generally one mole of the N-(2-chloroacetyl)-2',6'-dialkylaniline is reacted with a mole of the 4-bromo-3-alkoxy crotonate in a solvent with a hydrogen bromide acceptor such as KOH. The reaction mixture is refluxed until completion of the reaction. The reaction product is recovered by removing the volatile materials. Atmospheric, subatmospheric or superatmospheric pressured can be used, depending on the boiling point of the solvent used. Acetone is conveniently stripped at elevated temperatures and reduced pressure. The reaction product is worked up by conventional techniques.

The following example teaches the synthesis of a representative compound of this invention.

EXAMPLE I Preparation of Methyl-N-(2-chloroacetyl)-4-(2'-isopropyl-6'-methylphenylamino)-3-methoxy-2-butanoate ##STR4##

To a solution of 10.0 grams (g) (0.0443 mole) of N-(-2-chloroacetyl)-2'-isopropyl-6'-methylaniline and 20.0 g (0.096 mole) of methyl-4-bromo-3-methoxycrotonate in 25 milliliters (ml) of acetone was added 2 g of KOH. The solution was refluxed for one hour. The acetone was stripped off and 50 ml each of CH₂ Cl₂ and H₂ O was added. The aqueous phase was extracted with a total of three 50 ml portions of CH₂ Cl₂. The organic phase was combined, dried over magnesium sulfate and evaporated. The residue was taken up in 100 ml CCl₄, followed by the addition of 100 ml hexane with ice water cooling causing the precipitation of 10.2 g (66% yield) of the desired product free of the bromocrotonate as a tan solid, m.p. 156°-159° C. The assigned structure was supported by nmr and ir spectral data.

The following is a table of certain selected compounds that are preparable according to the procedure described herein. Compound numbers are assigned to each compound and are used throughout the remainder of the application.

                  TABLE I                                                          ______________________________________                                          ##STR5##                                                                        Com-                                                                         pound                                                                          Num-                                  N.sub.D.sup.30                           ber                                                                              R       R.sup.1   R.sup.2 R.sup.3                                                                             R.sup.4                                                                             or m.p. °C.                       ______________________________________                                         1     CH.sub.3  CH.sub.3  H    CH.sub.3                                                                            CH.sub.3                                                                            108-109                               2     CH.sub.3  CH.sub.3  H    CH.sub.3                                                                            C.sub.2 H.sub.5                                                                      85-100                               3     CH.sub.3  CH.sub.3  H    C.sub.2 H.sub.5                                                                     C.sub.2 H.sub.5                                                                     88-91                                 4     C.sub.2 H.sub.5                                                                          C.sub.2 H.sub.5                                                                          H    CH.sub.3                                                                            CH.sub.3                                                                            90-94                                 5     C.sub.2 H.sub.5                                                                          C.sub.2 H.sub.5                                                                          H    CH.sub.3                                                                            C.sub.2 H.sub.5                                                                     87-89                                 6     C.sub.2 H.sub.5                                                                          C.sub.2 H.sub.5                                                                          H    C.sub.2 H.sub.5                                                                     CH.sub.3                                                                            1.5194                                7     C.sub.2 H.sub.5                                                                          CH.sub.3  H    CH.sub.3                                                                            CH.sub.3                                                                             95-100                               8     C.sub.2 H.sub.5                                                                          CH.sub.3  H    CH.sub.2                                                                            C.sub.2 H.sub.5                                                                     1.5261                                9     C.sub.2 H.sub.5                                                                          CH.sub.3  H    C.sub.2 H.sub.5                                                                     CH.sub.3                                                                            80-83                                 10    C.sub.2 H.sub.5                                                                          CH.sub.3  H    C.sub.2 H.sub.5                                                                     C.sub.2 H.sub.5                                                                     76-78                                 11    CH(CH.sub.3).sub.2                                                                       CH.sub.3  H    CH.sub.3                                                                            CH.sub.3                                                                            156-159                               12    CH.sub.3  CH(CH.sub.3).sub.2                                                                       H    CH.sub.3                                                                            C.sub.2 H.sub.5                                                                     1.5335                                13    CH(CH.sub.3).sub.2                                                                       CH.sub.3  H    C.sub.2 H.sub.5                                                                     CH.sub.3                                                                             94-100                               14    CH.sub.3  CH(CH.sub.3).sub.2                                                                       H    C.sub.2 H.sub.5                                                                     C.sub.2 H.sub.5                                                                     64-70                                 15    C(CH.sub.3).sub.3                                                                        CH.sub.3  H    CH.sub.3                                                                            CH.sub.3                                                                             94-100                               16    C(CH.sub.3).sub.3                                                                        CH.sub.3  H    CH.sub.3                                                                            C.sub.2 H.sub.5                                                                      96-102                               17    CH.sub.3  C(CH.sub.3).sub.3                                                                        H    C.sub.2 H.sub.5                                                                     C.sub.2 H.sub.5                                                                     1.4931                                18    CH.sub.3  CH.sub.3  CH.sub.3                                                                            CH.sub.3                                                                            CH.sub.3                                                                            dark                                                                           brown                                                                          solid                                 19    CH.sub.3 O                                                                               CH.sub.3  H    C.sub.2 H.sub.5                                                                     CH.sub.3                                                                            70-80                                 ______________________________________                                    

Herbicidal Screening Tests

As previously mentioned, the herein described compounds are phytotoxic compounds which are useful and valuable in controlling various grass species either pre-emergence or pre-plant. Selected compounds of this invention were tested as such herbicides in the following manner.

Pre-emergence herbicide test. On the day preceding treatment, seeds of watergrass (WG) (Echinochloa crusgalli), velvetleaf (VL) (Abutilon theophrasti), Indian mustard (MD) (Brassica juncea) and curly dock (CD) (Rumex crispus) are planted in loamy sand soil in individual rows using one species per row across the width of a flat. Ample seeds are planted to give about 20 to 40 seedlings per row, after emergence, depending upon the size of the plants.

Using an analytical balance, 600 milligrams (mg) of the compound to be tested are weighed out on a piece of glassine weighing paper. The paper and compound are placed in a 60 milliliter (ml) wide-mouth clear bottle and dissolved in 45 ml of acetone or substituted solvent. Eighteen ml of this solution are transferred to a 60 ml wide-mouth clear bottle and diluted with 22 ml of a water and acetone mixture (19:1) containing enough polyoxyethylene sorbitan monolaurate emulsifier to give a final solution of 0.5% (v/v). The solution is then sprayed on a seeded flat on a linear spray table calibrated to deliver 80 gallons per acre (748 L/ha). The application rate is 4 lb/acre (4.48 Kg/ha).

After treatment, the flats are placed in the greenhouse at a temperature of 70° to 80° F. and watered by sprinkling. Two weeks after treatment, the degree of injury or control is determined by comparison with untreated check plants of the same age. The injury rating from 0 to 100% is recorded for each species as percent control with 0% representing no injury and 100% representing complete control.

The results of the tests are shown in the following Table II.

                  TABLE II                                                         ______________________________________                                         Post-Emergence Grass Herbicidal Activity                                       Application Rate - 4.48 kg/ha                                                  Compound              Compound                                                 Number    Watergrass  Number    Watergrass                                     ______________________________________                                         1          95         11        90                                             2         100         12        100                                            3          20         13        100                                            4         100         14        100                                            5         100         15        100                                            6          85         16        95                                             7         100         17        70                                             8         100         18        60                                             9         100         19        80                                             10         80                                                                  ______________________________________                                    

The compounds of the present invention are useful as grass herbicides, especially as post-emergence herbicides, and can be applied in a variety of ways at various concentrations. In practice, the compounds herein defined are formulated into herbicidal compositions, by admixture, in herbicidally effective amounts, with the adjuvants and carriers normally employed for facilitating the dispersion of active ingredients for agricultural applications, recognizing the fact that the formulation and mode of application of a toxicant may affect the activity of the materials in a given application. Thus, these active herbicidal compounds may be formulated as granules of relatively large particle size, as wettable powders, as emulsifiable concentrates, as powdery dusts, as solutions or as any of several other known types of formulations, depending upon the desired mode of application. Preferred formulations for pre-emergence herbicidal applications are wettable powders, emulsifiable concentrates and granules. These formulations may contain as little as about 0.5% to as much as about 95% or more by weight of active ingredient. A herbicidally effective amount depends upon the nature of the seeds or plants to be controlled and the rate of application varies from about 0.05 to approximately 25 pounds per acre, preferably from about 0.1 to about 10 pounds per acre.

Wettable powders are in the form of finely divided particles which disperse readily in water or other dispersants. The wettable powder is ultimately applied to the soil either as a dry dust or as a dispersion in water or other liquid. Typical carriers for wettable powders include fuller's earth, kaolin clays, silicas and other readily wet organic or inorganic diluents. Wettable powders normally are prepared to contain about 5% to about 95% of the active ingredient and usually also contain a small amount of wetting, dispersing, or emulsifying agent to facilitate wetting and dispersion.

Emulsifiable concentrates are homogeneous liquid compositions which are dispersible in water or other dispersant, and may consist entirely of the active compound with a liquid or solid emulsifying agent, or may also contain a liquid carrier, such as xylene, heavy aromatic naphtha, isophorone and other non-volatile organic solvents. For herbicidal application, these concentrates are dispersed in water or other liquid carrier and normally applied as a spray to the area to be treated. The percentage by weight of the essential active ingredient may vary according to the manner in which the composition is to be applied, but in general comprises about 0.5% to 95% of active ingredient by weight of the herbicidal composition.

Granular formulations wherein the toxicant is carried on relatively coarse particles, are usually applied without dilution to the area in which suppression of vegetation is desired. Typical carriers for granular formulations include sand, fuller's earth, bentonite clays, vermiculite, perlite and other organic or inorganic materials which absorb or which may be coated with the toxicant. Granular formulations normally are prepared to contain about 5% to about 25% of active ingredients which may include surface-active agents such as wetting agents, dispersing agents or emulsifiers; oil such as heavy aromatic naphthas, kerosene or other petroleum fractions, or vegetable oils; and/or stickers such as dextrins, glue or synthetic resins.

Typical wetting, dispersing or emulsifying agents used in agricultural formulations include, for example, the alkyl and alkylaryl sulfonates and sulfates and their sodium salts; polyhydroxy alcohols; and other types of surface-active agents, many of which are available in commerce. The surface-active agent, when used, normally comprises from 0.1% to 15% by weight of the herbicidal composition.

Dusts, which are free-flowing admixtures of the active ingredient with finely divided solids such as talc, clays, flours and other organic and inorganic solids which act as dispersants and carriers for the toxicant, are useful formulations for soil-incorporating application.

Pastes, which are homogeneous suspensions of a finely divided solid toxicant in a liquid carrier such as water or oil, are employed for specific purposes. These formulations normally contain about 5% to about 95% of active ingredient by weight, and may also contain small amounts of a wetting, dispersing or emulsifying agent to facilitate dispersion. For application, the pastes are normally diluted and applied as a spray to the area to be affected.

Other useful formulations for herbicidal applications include simple solutions of the active ingredient in a dispersant in which it is completely soluble at the desired concentration, such as acetone, alkylated naphthalenes, xylene and other organic solvents. Pressurized sprays, typically aerosols, wherein the active ingredient is dispersed in finely-divided form as a result of vaporization of a low boiling dispersant solvent carrier, such as the Freons, may also be used.

The phytotoxic compositions of this invention are applied to the plants in the conventional manner. Thus, the dust and liquid compositions can be applied to the plant by the use of power-dusters, boom and hand sprayers and spray dusters. The compositions can also be applied from airplanes as a dust or a spray because they are effective in very low dosages. In order to modify or control growth of germinating seeds or emerging seedlings, as a typical example, the dust and liquid compositions are applied to the soil according to conventional methods and are distributed in the soil to a depth of at least 1/2 inch below the soil surface. It is not necessary that the phytotoxic compositions be admixed with the soil particles since these compositions can also be applied merely by spraying or sprinkling the surface of the soil. The phytotoxic compositions of this invention can also be applied by addition to irrigation water supplied to the field to be treated. This method of application permits the penetration of the compositions into the soil as the water is absorbed therein. Dust compositions, granular compositions or liquid formulations applied to the surface of the soil can be distributed below the surface of the soil by conventional means such as discing, dragging or mixing operations.

The phytotoxic compositions of this invention can also contain other additaments, for example, fertilizers and other herbicides, pesticides and the like, used as adjuvant or in combination with any of the above-described adjuvants. Other phytotoxic compounds useful in combination with the abovedescribed compounds include, for example, 2,4-dichlorophenoxyacetic acids, 2,4,5-trichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid and the salts, esters and amides thereof, triazine derivatives, such as 2,4-bis(3-methoxypropylamino)-6-methylthio-s-triazine, 2-chloro-4-ethylamino-6-isopropylamino-s-triazine, and 2-ethylamino-4-isopropyl-amino-6-methyl-mercapto-s-triazine; urea derivatives, such as 3-(3,5-dichlorophenyl)-1,1-dimethylurea and 3-(p-chlorophenyl)-1,1-dimethylurea; and acetamides such as N,N-diallyl-α-chloroacetamide, and the like; benzoic acids such as 3-amino-2,5-dichlorobenzoic acid; thiocarbamates such as S-propyl N,N-dipropylthiocarbamate, S-ethyl N,N-dipropylthiocarbamate, S-ethyl cyclohexylethylthiocarbamate, S-ethyl hexahydro-1H-azepine-1-carbothioate and the like; anilines such as 4-(methylsulfonyl)-2,6-dinitro-N,N-substituted aniline, 4-trifluoromethyl-2,6-dinitro-N,N-di-n-propyl aniline, 4-trifluoromethyl-2,6-dinitro-N-ethyl-N-butyl aniline, 2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid, 2-[1-(ethoxyamino)butyl]-5-[2-ethylthio)propyl]-3-hydroxy-2-cyclohexene-1-one, (±)-butyl- 2-[4-[(5-trifluoromethyl)-2-pyridinyl)oxy]phenoxy]propanate, sodium 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate, 3-isopropyl-1H-2,1,3-benzothiadiazine-4(3H)-one-2,2-dioxide, and 4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one or (4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one). Fertilizers useful in combination with the active ingredients include, for example, ammonium nitrate, urea and superphosphate. Other useful additaments include materials in which plant organisms take root and grow such as compost, manure, humus, sand, and the like. 

We claim:
 1. A compound having the structural formula ##STR6## wherein R is Chd 1-C₄ alkyl; R¹ is C₁ -C₄ alkyl; R² is hydrogen or methyl; R³ is methyl or ethyl; and R⁴ is C₁ -C₄ alkyl.
 2. The compound of claim 1 wherein R is methyl or ethyl, R¹ is methyl or ethyl, R² is hydrogen, R³ is methyl or ethyl and R⁴ is methyl or ethyl.
 3. The compound of claim 1 wherein R is ethyl, R¹ is methyl, R² is hydrogen, R³ is methyl and R⁴ is methyl.
 4. The compound of claim 1 wherein R is methyl, R¹ is methyl, R² is hydrogen, R³ is methyl and R⁴ is methyl.
 5. The compound of claim 1 wherein R is ethyl, R¹ is ethyl, R² is hydrogen, R³ is methyl and R⁴ is ethyl.
 6. The method of controlling grasses comprising applying pre-emergence or pre-plant to the area where control is desired, an herbicidally effective amount of a compound having the formula ##STR7## wherein R is C₁ -C₄ alkyl; R¹ is C₁ -C₄ alkyl; R² is hydrogen or methyl; R³ is methyl or ethyl; and R⁴ is C₁ -C₄ alkyl.
 7. The method of claim 6 wherein R is methyl or ethyl, R¹ is methyl or ethyl, R² is hydrogen, R³ is methyl or ethyl and R⁴ is methyl or ethyl.
 8. The method of claim 6 wherein R is ethyl, R¹ is methyl, R² is hydrogen, R³ is methyl and R⁴ is methyl.
 9. The method of claim 6 wherein R is methyl, R¹ is methyl, R² is hydrogen, R³ is methyl and R⁴ is methyl.
 10. The method of claim 6 wherein R is ethyl, R¹ is ethyl, R² is hydrogen, R³ is methyl and R⁴ is ethyl. 